1. Field of the Invention
The present invention relates to a remotely actuated towline throwing device. Specifically, the present invention relates to a towline throwing gun which may be permanently mounted on an unmanned sea going vessel such as a barge and with this throwing gun remotely actuated to provide for a rescue of the barge in the event of a separation of the original towline which is being used to tow the barge.
2. Description of the Prior Art
In the current operation of tugboats in the open ocean, the tugboat and and towed vessel, such as a barge, is interconnected through the use of a heavy towline. This towline may be made of wire rope of synthetic rope which is attached at one end to the barge and at the other end to the tugboat so that the tugboat provides for the propulsion to move the barge through the water to its desired destination.
One difficulty which can arise is a breakage or separation of the towline or a breakage of a towline connection. When the barge is actually in the open ocean, this can occur because of the heavy loads on the towlines and connections and because the barges are often being towed through stormy conditions which creates turbulent seas. Because the tow unit is normally unmanned the tugboat must somehow reconnect a towline to prevent the towed unit from drifting or from grounding. Since, as indicated above, the breakage of the towline often occurs under storm conditions, the recapture of the towed unit presents a serious and dangerous problem.
If the weather as well as the seas is calm, it would be possible for the tugboat to maneuver close to the drifting barge so that personnel can be sent out to board the barge to assist in re-establishing a new towline. During stormy weather and high seas, it would be dangerous to try to have personnel transferred from the tug to the barge, or even to maneuver the tugboat too close to the barge. Actually, even with calm seas it would be safer not to have to send personnel from the tugboat to the barge.
In order to eliminate the need for personnel to transfer from the tugboat to the barge, the prior art has provided a method of recapturing the barge by the use of an insurance line or wire. This insurance line or wire forms an auxiliary or spare towing cable which is laid out or stored on the barge and has one end of the insurance line made fast to a towing pad. The other end of the insurance line is connected to a buoyant float line and with this buoyant float line streamed astern of the barge.
The storage of the insurance line may take a variety of different forms. For example, one type of barge which is currently employed in the Caribbean are generally referred to as triple deck barges. These barges are quite heavy because of their height and a single tug normally tows only one barge at a time. With this type of structure the insurance line extends from the tow pad at the front of the barge and along the side of the barge where it is held by clips. Additional length of this insurance line may be stored at the back of barge by folding the towline back and forth and with the folded line again being held in position by clips. A float line is connected to the insurance line and extends from the back of the barge to a permanent float in the water. If the original towline should break, the tugboat, since it is towing only one barge at a time, is normally free to try to manuever within 35 or 40 feet of the stern of the barge to try to pick up the floating line.
On the Westcoast, a great deal of towing is accomplished by the use of two separate flat barges towed from a single tugboat. Each barge is connected to the tugboat through the use of a separate tow wire and with the tugboat including a double drum winch to support both tow wires. Since the towline which extends from the tugboat to any barge should assume the shape of a catenary, the towline of the end barge will actually pass safely beneath the forward barge. Should one or the other of the towlines part, it now becomes necessary for the tug to try to manuever in close to the separated barge, but with the other barge still attached to the stern.
The attached barge, of course, limits the tugboat's ability to manuever and normally any pickup of the drifting barge must be done across its bow or stern and into the wind. This is because a drifting barge normally lays in the trough of the seas and swells and drifts sideways with the wind. This is why the pickup must be across the drifting tugs bow or stern as opposed to the side where the barge can drift down onto the tug and cause a collision. With the large flat barges used on the westcoast, the insurance line is normally stored on the top surface of the barge and along one edge. Again, the floating line drifts behind the barge.
With either of the two prior art systems described above, if the tugboat can manuever close enough to pick up the floating line, then the floating line is pulled on board the tugboat to theoretically pull in the insurance line. Since normally a portion of the insurance line is secured in position by clips, these clips must be of the type which either release or break as the floating line is pulled to deploy the insurance line. If all goes well, the insurance line is eventually reconnected to the tugboat and the barge is again under tow.
The above described prior art system has a number of serious limitations. First the prior art system depends on the tugboat being able to manuever close enough to capture the floating line. As indicated above, this may be difficult if the original line parted during stormy seas. Moreover, even in calmer weather, this system still requires that the tugboat be moved quite close to the barge and there is always the danger of a collision.
Another difficiency with the prior art system is that the insurance line is normally located either on the deck or the side of the barge and is thereby continually exposed to the elements and to salt water. Because of this exposure, the insurance line corrodes and can be of inadequate strength to sustain the forces of full towage when the need arises. Instead of serving as an emergency line, the insurance line upon being connected to the tugboat, may itself break and the problem of the loose barge has not been solved.
Another difficiency with the prior art system is the use of the float line that is trailed astern of the barge. This float line can be a very weak link snnce it is also exposed to the ultraviolet elements and can lose strength. This line may end up being so weak that it separates before the insurance line can even be brought on board the tugboat.
Even if the float line is of sufficient strength, the float line must be used in order to pull the insurance wire on baord the tug. However, the float line extends from the stern of the ship and the attached portion of the insurance line is located at the bow of the barge, and with an intermediate portion of the insurance line extending from the bow to the stern and connected to the float line. This intermediate portion of the insurance line must be cleared forward without hanging up or interfering with various portions of the barge which are attached to the deck of the barge and project upward. These portions may include expansions, bitts, cleats, chocks, etc.
It can be seen, therefore, that the prior art devices often fail to provide a reliable back up system to produce an emergency re-establishment of a towline between a tugboat and a barge in all types of weather conditions and which can operate reliably over long periods of time.